Biomedical Engineering Reference
In-Depth Information
providing detailed information about size or composition, while others are “personal” at the expense
of detailed information. The benefit of acquiring detailed size distribution data online (especially
of number size distributions) is that such information can be easily and accurately converted into
almost any other physical metric (except shape, which requires additional parameters). Keeping in
mind the open-ended discussion about appropriate metrics; number size distribution data are thus
the most valuable record that leaves the door open to
a posteriori
tests of new hypotheses concern-
ing health risks of engineered nanomaterial.
In the past two decades, methods providing direct chemical, compositional, or biological infor-
mation of airborne particles, usually on the basis of optical or mass spectroscopy, have received a
major push in the field of atmospheric sciences and most recently, also in response to global security
threats [77]. However, these devices are often quite expensive and complex, and the technology has
not yet filtered down to affordable levels for health hazard evaluation.
Generally, one of the real challenges ahead for engineered nanomaterial monitoring and health
risk assessment is (a) to redesign portable or personal and affordable “engineered nanomaterial-
capable” instruments, (b) to expand the sensing technology available for engineered nanomaterial
detection by adopting new options with realistic potential for real-time measurement and compact
design, and (c) to extend the metrics into new areas such as CNT shape identification as well as
surface chemical or catalytic properties. These latter concepts are especially interesting, since they
have the potential of distinguishing engineered nanomaterial against background particles via spe-
cial morphological features or function (not composition!).
The inability to separate engineered nanomaterial from the background NPs by straightforward
concentration and size distribution measurements makes it impossible or at least highly problematic
to set occupational exposure limits (OELs) for engineered nanomaterial. Harmful health effects,
such as increased cardiac and pulmonary mortality, of ambient fine particles have been emphasized.
Wide utilization of nanotechnologies globally is though a novel phenomenon, and is likely to have
an impact on human health on a global scale in future. Besides, exposure to particle aerosols out-
doors or indoors is in most cases exposure to a mixture of particles with a wide range of diameters
and, hence, the importance of assessing the impact of the particle size range on effects on human
health is a special challenge. There are thorough data, which suggest that exposure to UFPs, the
ubiquitous background nanosized particles, may be especially harmful in inducing harmful health
effects such as pulmonary inflammation, effects on circulation, and even increased cardiac mortal-
ity [78]. When assessing the health impact of engineered nanomaterial in occupational and other
environments, the distinction between background ultrafine or NPs from engineered nanomaterial
becomes especially important, because the ability of dissecting these effects is the prerequisite of
setting of occupational exposure limits.
Each of the above avenues addresses an important demand: (i) making the current engineered
nanomaterial monitoring technology more compact, more affordable, and more versatile will pro-
vide imminent short-term solutions required by toxicologists and the inhalation exposure commu-
nity; (ii) new sensing technology will have a midterm effect by providing sophisticated measurement
options for very small particles that can be adapted to the needs of aerosol-monitoring technology; and
(iii) finally, the need of devices capable of capturing entirely new properties will provide new tools to
characterize airborne-engineered nanomaterial. It will be important for these new devices to provide
real-time and online data. However, the foregoing discussion also makes it clear than an ideal, all-
purpose monitoring method will only become available (if it ever becomes available), once a clear link
between health effects and engineered nanomaterial characteristics is well established for a majority
of exposure scenarios, and this will only happen after sufficient data have been collected and analyzed.
19.7.3 h
azard
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haracterIzatIoN
In this context, the discussion on health effects of engineered nanomaterial will be limited to
the translocation of engineered nanomaterials in the body, and their effects on the lungs, on the
